Extension of the reach of tractor-mounted cutting equipment is needed to take fuller advantage of the mobility and built-in hydraulic power systems offered by tractors. In particular, a capability for reaching over fences, guard rails, and other obstacles would reduce requirements for use of hand-held equipment in the final step of many cutting jobs. Support of cutting devices for deployment in other rough spots such as in and around ditches and on slopes is also desired.
Various arrangements for mounting of mowers on tractors are shown in prior patents. U.S. Pat. No. 4,048,789, issued Sep. 20, 1977, to Cartner, discloses a tractor-mounted mower attachment using a hydraulically articulated linkage system enabling pivoting motion to carry out horizontal, vertical, and angular movement of the mower. Jolls, in U.S. Pat. No. 3,274,762, issued Sep. 27, 1966, discloses a mower-supporting arm adjustably mounted on a vertical bracket and articulated to provide for pivoting and telescoping movement as required for a desired location of the mower cutter bar. U.S. Pat. No. 4,956,965, issued Sep. 10, 1990, to Parsons, discloses a boom attachment pivotally connected to an upstanding support so as to allow a mower to be moved to a position on either side of the tractor. A boom supporting a mower for swinging around vertically and horizontally as well as for telescoping is shown in U.S. Pat. No. 3,949,539, issued Apr. 13, 1976, to Cartner. Mounting of a grass trimmer on an articulated arm carried by a special purpose vehicle is disclosed in U.S. Pat. No. 4,663,920, issued May 12, 1987, to Shovhoj, the arm in this patent being designed for hand manipulation of a parallelogram structure rather than for hydraulic operation. While the devices shown in these patents enable maneuvering of tractor-mounted mowers or trimmer units into desired cutting positions with respect to the ground, they do not provide for lifting the cutting device high enough to reach over and clear obstacles such as fences. In addition to extending over obstacles, into low spots and along slopes, the arm and attached cutter should allow for horizontal movement for a substantial distance to facilitate cutting a wide area, and it should cut a path along a fence on the side across from the tractor while tracking forward or rearward with the tractor.